Plane Wave

14,000,000 Leading Edge Experts on the ideXlab platform

Scan Science and Technology

Contact Leading Edge Experts & Companies

Scan Science and Technology

Contact Leading Edge Experts & Companies

The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform

Arkady A Tseytlin - One of the best experts on this subject based on the ideXlab platform.

  • exactly solvable model of superstring in Plane Wave ramond ramond background
    Physical Review D, 2002
    Co-Authors: R R Metsaev, Arkady A Tseytlin
    Abstract:

    We describe in detail the solution of type IIB superstring theory in the maximally supersymmetric Plane-Wave background with constant null Ramond-Ramond 5-form field strength. The corresponding light-cone Green-Schwarz action found by Metsaev is quadratic in both bosonic and fermionic coordinates. We obtain the light-cone Hamiltonian and the string representation of the corresponding supersymmetry algebra. The superstring Hamiltonian has a ``harmonic-oscillator'' form in both the string oscillator and the zero-mode parts and thus has a discrete spectrum. We analyze the structure of the zero-mode sector of the theory, establishing the precise correspondence between the lowest-lying ``massless'' string states and the type IIB supergravity fluctuation modes in the Plane-Wave background. The zero-mode spectrum has a certain similarity to the supergravity spectrum in ${\mathrm{AdS}}_{5}\ifmmode\times\else\texttimes\fi{}{\mathrm{S}}^{5}$ background of which the Plane-Wave background is a special limit. We also compare the Plane-Wave string spectrum with the expected form of the light-cone gauge spectrum of the ${\mathrm{AdS}}_{5}\ifmmode\times\else\texttimes\fi{}{\mathrm{S}}^{5}$ superstring.

  • exactly solvable model of superstring in Plane Wave ramond ramond background
    2002
    Co-Authors: R R Metsaev, Arkady A Tseytlin
    Abstract:

    We describe in detail the solution of type IIB superstring theory in the maximally supersymmetric Plane-Wave background with constant null Ramond-Ramond 5-form field strength. The corresponding light-cone Green-Schwarz action found in hep-th/0112044 is quadratic in both bosonic and fermionic coordinates. We find the spectrum of the light-cone Hamiltonian and the string representation of the supersymmetry algebra. The superstring Hamiltonian has a ``harmonic-oscillator'' form in both the string-oscillator and the zero-mode parts and thus has discrete spectrum in all 8 transverse directions. We analyze the structure of the zero-mode sector of the theory, establishing the precise correspondence between the lowest-lying ``massless'' string states and the type IIB supergravity fluctuation modes in the Plane-Wave background. The zero-mode spectrum has certain similarity to the supergravity spectrum in AdS_5 x S^5 of which the Plane-Wave background is a special limit. We also compare the Plane-Wave string spectrum with expected form of the light-cone gauge spectrum of superstring in AdS_5 x S^5.

Charles F Caskey - One of the best experts on this subject based on the ideXlab platform.

  • fast low frequency Plane Wave imaging for ultrasound contrast imaging
    Ultrasound in Medicine and Biology, 2018
    Co-Authors: Jiro Kusunose, Charles F Caskey
    Abstract:

    Abstract Plane-Wave ultrasound contrast imaging offers a faster, less destructive means for imaging microbubbles compared with traditional ultrasound imaging. Even though many of the most acoustically responsive microbubbles have resonant frequencies in the lower-megahertz range, higher frequencies (>3 MHz) have typically been employed to achieve high spatial resolution. In this work we implement and optimize low-frequency (1.5-4 MHz) Plane-Wave pulse inversion imaging on a commercial, phased-array imaging transducer in vitro and illustrate its use in vivo by imaging a mouse xenograft model. We found that the 1.8-MHz contrast signal was about four times that acquired at 3.1 MHz on matched probes and nine times greater than echoes received on a higher-frequency probe. Low-frequency imaging was also much more resilient to motion. In vivo, we could identify sub-millimeter vasculature inside a xenograft tumor model and easily assess microbubble half-life. Our results indicate that low-frequency imaging can provide better signal-to-noise because it generates stronger non-linear responses. Combined with high-speed Plane-Wave imaging, this method could open the door to super-resolution imaging at depth, while high power pulses could be used for image-guided therapeutics.

R R Metsaev - One of the best experts on this subject based on the ideXlab platform.

  • exactly solvable model of superstring in Plane Wave ramond ramond background
    Physical Review D, 2002
    Co-Authors: R R Metsaev, Arkady A Tseytlin
    Abstract:

    We describe in detail the solution of type IIB superstring theory in the maximally supersymmetric Plane-Wave background with constant null Ramond-Ramond 5-form field strength. The corresponding light-cone Green-Schwarz action found by Metsaev is quadratic in both bosonic and fermionic coordinates. We obtain the light-cone Hamiltonian and the string representation of the corresponding supersymmetry algebra. The superstring Hamiltonian has a ``harmonic-oscillator'' form in both the string oscillator and the zero-mode parts and thus has a discrete spectrum. We analyze the structure of the zero-mode sector of the theory, establishing the precise correspondence between the lowest-lying ``massless'' string states and the type IIB supergravity fluctuation modes in the Plane-Wave background. The zero-mode spectrum has a certain similarity to the supergravity spectrum in ${\mathrm{AdS}}_{5}\ifmmode\times\else\texttimes\fi{}{\mathrm{S}}^{5}$ background of which the Plane-Wave background is a special limit. We also compare the Plane-Wave string spectrum with the expected form of the light-cone gauge spectrum of the ${\mathrm{AdS}}_{5}\ifmmode\times\else\texttimes\fi{}{\mathrm{S}}^{5}$ superstring.

  • exactly solvable model of superstring in Plane Wave ramond ramond background
    2002
    Co-Authors: R R Metsaev, Arkady A Tseytlin
    Abstract:

    We describe in detail the solution of type IIB superstring theory in the maximally supersymmetric Plane-Wave background with constant null Ramond-Ramond 5-form field strength. The corresponding light-cone Green-Schwarz action found in hep-th/0112044 is quadratic in both bosonic and fermionic coordinates. We find the spectrum of the light-cone Hamiltonian and the string representation of the supersymmetry algebra. The superstring Hamiltonian has a ``harmonic-oscillator'' form in both the string-oscillator and the zero-mode parts and thus has discrete spectrum in all 8 transverse directions. We analyze the structure of the zero-mode sector of the theory, establishing the precise correspondence between the lowest-lying ``massless'' string states and the type IIB supergravity fluctuation modes in the Plane-Wave background. The zero-mode spectrum has certain similarity to the supergravity spectrum in AdS_5 x S^5 of which the Plane-Wave background is a special limit. We also compare the Plane-Wave string spectrum with expected form of the light-cone gauge spectrum of superstring in AdS_5 x S^5.

M C Payne - One of the best experts on this subject based on the ideXlab platform.

  • nonorthogonal generalized wannier function pseudopotential Plane Wave method
    Physical Review B, 2002
    Co-Authors: Chriskriton Skylaris, Arash A Mostofi, Peter D Haynes, Oswaldo Dieguez, M C Payne
    Abstract:

    We present a reformulation of the Plane-Wave pseudopotential method for insulators. This new approach allows us to perform density-functional calculations by solving directly for “nonorthogonal generalized Wannier functions” rather than extended Bloch states. We outline the theory on which our method is based and present test calculations on a variety of systems. Comparison of our results with a standard Plane-Wave code shows that they are equivalent. Apart from the usual advantages of the Plane-Wave approach such as the applicability to any lattice symmetry and the high accuracy, our method also benefits from the localization properties of our functions in real space. The localization of all our functions greatly facilitates the future extension of our method to linear-scaling schemes or calculations of the electric polarization of crystalline insulators.

  • population analysis of Plane Wave electronic structure calculations of bulk materials
    Physical Review B, 1996
    Co-Authors: M D Segall, Rajiv Shah, Chris J Pickard, M C Payne
    Abstract:

    {ital Ab} {ital initio} Plane-Wave electronic structure calculations are widely used in the study of bulk materials. A technique for the projection of Plane-Wave states onto a localized basis set is used to calculate atomic charges and bond populations by means of Mulliken analysis. We analyze a number of simple bulk crystals and find correlations of overlap population with covalency of bonding and bond strength, and effective valence charge with ionicity of bonding. Thus, we show that the techniques described in this paper may be usefully applied in the field of solid state physics. {copyright}{ital 1996 The American Physical Society.}

  • population analysis of Plane Wave electronic structure calculations of bulk materials
    Physical Review B, 1996
    Co-Authors: M D Segall, Rajiv Shah, Chris J Pickard, M C Payne
    Abstract:

    Ab initio Plane-Wave electronic structure calculations are widely used in the study of bulk materials. A technique for the projection of Plane-Wave states onto a localized basis set is used to calculate atomic charges and bond populations by means of Mulliken analysis. We analyze a number of simple bulk crystals and find correlations of overlap population with covalency of bonding and bond strength, and effective valence charge with ionicity of bonding. Thus, we show that the techniques described in this paper may be usefully applied in the field of solid state physics. \textcopyright{}1996 The American Physical Society.

Weng Cho Chew - One of the best experts on this subject based on the ideXlab platform.

  • A Low-Frequency Stable Broadband Multilevel Fast Multipole Algorithm Using Plane Wave Multipole Hybridization
    IEEE Transactions on Antennas and Propagation, 2018
    Co-Authors: Tian Xia, Ling Ling Meng, Qin S. Liu, Hui H. Gan, Weng Cho Chew
    Abstract:

    We propose a broadband multilevel fast multipole algorithm using hybridization of the Plane Wave and the multipole expansions of Green’s function in the analysis of 3-D electromagnetic problems. In the proposed method, the diagonal Plane-Wave expansion is used for low order harmonics, which captures most of the propagating spectrums, while the dense multipole expansion is used for high order harmonics, which captures most of the evanescent spectrums. By analyzing the errors and choosing the numbers of harmonics accordingly in the Plane Wave and the multipole expansions, the method is free of low-frequency breakdown and remains accurate at arbitrarily low frequencies, which is similar to the dense fast multipole algorithm (FMA). Meanwhile, the method reduces to the conventional diagonal FMA as the frequency increases. Therefore, it can be regarded as the generalization of the conventional dense and diagonal FMAs. Numerical studies in this paper show that very high accuracies can be achieved using the method.

  • low frequency fast inhomogeneous Plane Wave algorithm lf fipwa
    Microwave and Optical Technology Letters, 2004
    Co-Authors: Li Jun Jiang, Weng Cho Chew
    Abstract:

    A new method, the low-frequency fast inhomogeneous Plane-Wave algorithm (LF-FIPWA) is presented to extend the traditional multilevel fast multipole algorithm (MLFMA) and fast inhomogeneous Plane-Wave algorithm (FIPWA) seamlessly into the low-frequency range. It uses evanescent-Wave extrapolation and translation techniques to overcome the low-frequency breakdown problem. The accuracy can be well controlled over a broad frequency range. Numerical examples show the effectiveness of this new algorithm. © 2004 Wiley Periodicals, Inc. MicroWave Opt Technol Lett 40: 117–122, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11302

  • fast inhomogeneous Plane Wave algorithm for scattering from objects above the multilayered medium
    IEEE Transactions on Geoscience and Remote Sensing, 2001
    Co-Authors: Weng Cho Chew
    Abstract:

    A previously developed fast inhomogeneous Plane Wave algorithm is adapted to the analysis of the scattering from the objects above a multilayered medium. Based on the similarity of the inhomogeneous Plane Wave expansion of the Green's function encountered in the layered medium study to its free space counterpart, the proper steepest descent path can be defined. By using the interpolation and extrapolation techniques, the translation matrix is diagonalized. The contributions of the pole and branch point, resulting from the deformation of the integration path, can be handled easily. Comparing with the previously developed methods in this area, this algorithm is simpler, more efficient, and more general. The multilevel fast inhomogeneous Plane Wave algorithm has been implemented and the numerical results show that O(N log N) computational complexity of the algorithm is achieved. The algorithm is validated by comparing the results from a conventional method of moments program.